Removing cats

Blackwell808

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Hey everyone, will I need to be retuned if I remove my cats? The car has an ARH longtube system but id like to remove the cats for a little bit more flow and loudness. Magnaflow mufflers will still keep a good tone and not stupid loud. But I do not have any down stream sensors. I have my up stream and afr sensor and that’s it. So technically it shouldn’t need a retune correct? Feel free to correct me if I am wrong. Thanks!
 

shurur

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Not to pick a fight or anything, but I am having a hard time understanding why removing cats from a very good exhaust setup is all that important to you.

Also IMO with the EPA clamping down on exhaust systems, you are asking for trouble..inspection or not.

I guess you could cut them out and clamp on straights to see what it sounds like. My guess is that you are not going to like it, as the cats act as resonators and are part of the sound, not just part of the loudness.
 

hotcobra03

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When I installed long tubes
I got matching hi flow cat pipe

Was quiet

I than got the off road matching pipe.

Off road woke up the exhaust but
It also woke up the throttle response


I kept every part for if any reason to go back. Even all the stock parts that came off
 

Blackwell808

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Because to me, cats are somewhat restrictive and unnecessary. The car is insured as classic anyways so EPA can’t technically do shit about it since I’m exempt from emissions on it. I’m not dogging the setup I just want the car to be a touch louder. I don’t think cats are what set the tone but more the mufflers dictate that. I would keep my current pipe and have a complete new x pipe made custom
Not to pick a fight or anything, but I am having a hard time understanding why removing cats from a very good exhaust setup is all that important to you.

Also IMO with the EPA clamping down on exhaust systems, you are asking for trouble..inspection or not.

I guess you could cut them out and clamp on straights to see what it sounds like. My guess is that you are not going to like it, as the cats act as resonators and are part of the sound, not just part of the loudness.
fo
Not to pick a fight or anything, but I am having a hard time understanding why removing cats from a very good exhaust setup is all that important to you.

Also IMO with the EPA clamping down on exhaust systems, you are asking for trouble..inspection or not.

I guess you could cut them out and clamp on straights to see what it sounds like. My guess is that you are not going to like it, as the cats act as resonators and are part of the sound, not just part of the loudness.
Not to pick a fight or anything, but I am having a hard time understanding why removing cats from a very good exhaust setup is all that important to you.

Also IMO with the EPA clamping down on exhaust systems, you are asking for trouble..inspection or not.

I guess you could cut them out and clamp on straights to see what it sounds like. My guess is that you are not going to like it, as the cats act as resonators and are part of the sound, not just part of the loudness.
 

01yellercobra

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There have been dyno tests that show cats aren't as restrictive as people think. At least the high flow cats. And cats do affect sound. They're essentially a small muffler.
 

Blackwell808

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There have been dyno tests that show cats aren't as restrictive as people think. At least the high flow cats. And cats do affect sound. They're essentially a small muffler.
And that’s part of my point to the post here. I want the car a touch louder but not drastically. I know if I switch to slp or borla it’ll probably end up being too loud
 

909venm

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And that’s part of my point to the post here. I want the car a touch louder but not drastically. I know if I switch to slp or borla it’ll probably end up being too loud

Cats even a single set like you are using make a massive difference in volume. Unless they are the full body magnaflow’s aka the “street” system it is going to be loud. Mine are only slightly quieter than stingers were on my catless setup. But i run factory manifolds.
 

Blackwell808

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Cats even a single set like you are using make a massive difference in volume. Unless they are the full body magnaflow’s aka the “street” system it is going to be loud. Mine are only slightly quieter than stingers were on my catless setup. But i run factory manifolds.
Not sure what my magnaflow are exactly but the size of the muffler itself is fairly big. But again would I need a retune?
 

909venm

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Not sure what my magnaflow are exactly but the size of the muffler itself is fairly big. But again would I need a retune?

Someone will correct me but I believe you would need one. I know on a otherwise factory car simply removing the cats makes it leaner (or richer? I forget) and is why people say to get a tune. If you have a wideband theres no harm going and giving it a test run.
 

Blackwell808

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Someone will correct me but I believe you would need one. I know on a otherwise factory car simply removing the cats makes it leaner (or richer? I forget) and is why people say to get a tune. If you have a wideband theres no harm going and giving it a test run.
I do have wideband luckily. It’s not something I’m in a rush of doing. More of just tossing the idea around
 

OSU34

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No you do not need a retune. Your upstream sensors are adjusting everything - anything after that (if they are turned off) it doesn’t matter.


Sent from my iPhone using svtperformance.com
 

cj428mach

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No you do not need a retune. Your upstream sensors are adjusting everything - anything after that (if they are turned off) it doesn’t matter.


Sent from my iPhone using svtperformance.com


O2 sensors don't do anything for WOT though which is where you need AFR correct. Although I agree, you won't need a tune other than to turn off an SES light.
 

stangfreak

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Because to me, cats are somewhat restrictive and unnecessary. The car is insured as classic anyways so EPA can’t technically do shit about it since I’m exempt from emissions on it. I’m not dogging the setup I just want the car to be a touch louder. I don’t think cats are what set the tone but more the mufflers dictate that. I would keep my current pipe and have a complete new x pipe made custom

fo

The epa doesn't care if its a classic or not. They are going after everyone
 

stangfreak

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If you are building a high hp car, question is, how long with those cats last under high boost. and how many will you be replacing.
 

biminiLX

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To answer the OP question, with free flowing exhaust and the rear/downstream oxygen sensors inactivated, no retune necessary.
May want to datalog or check WOT A/F and even see if boost effected (might decrease up to one full pound).
I actually think full aftermarket exhaust with cats sounds deeper. Removing the cats definitely makes it louder as it serves as a mini muffler. Only reason I prefer free flowing exhaust on performance applications, especially if boosted, is eliminating the risk of clogged/melted/failed cats.
I think the stink if no cats is much worse on pump 91/93 than Ethanol.
Good luck
-J
 

9397SVTs

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To answer the OP question, with free flowing exhaust and the rear/downstream oxygen sensors inactivated, no retune necessary.
May want to datalog or check WOT A/F and even see if boost effected (might decrease up to one full pound).
I actually think full aftermarket exhaust with cats sounds deeper. Removing the cats definitely makes it louder as it serves as a mini muffler. Only reason I prefer free flowing exhaust on performance applications, especially if boosted, is eliminating the risk of clogged/melted/failed cats.
I think the stink if no cats is much worse on pump 91/93 than Ethanol.
Good luck
-J

I agree.

With my Cobra, all I smell is.........
images(97).jpg
 

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